Vacuum pumping apparatus



May 3, 1960 Filed Dec. 10, 1956 P. SADLER VACUUM PUMPING APPARATUS 4Sheets-Sheet 1 "IE- a "warren 1 5-212 S Amen Wm M, Mwawh 1960 P. SADLER2,935,243

VACUUM PUMPING APPARATUS Filed Dec. 10, 1956 4 Sheets-Sheet 2 mvzumTETER S ADLER ATTEF'NEYS May 3, 1960 P. SADLER 2,935,243

VACUUM PUMPING APPARATUS Filed Dec. 10, l956 4 Sheets-Sheet 5 mvzwronTETER SADLER L m,wwwm

ATToRHEYs May 3, 1960 P. SADLER 2,935,243

VACUUM PUMPING APPARATUS Filed Dec. 10, 1956 I 4 Sheets-Sheet 4 INVENT0R 'PETER S ADLER Wm M, WW 2%)! ATTORNEYS United States Patent G VACUUMPUMPING APPARATUS Peter Sadler, Pcndleton, Salford, England, assignor toN.G.N. Electrical Limited, Patricroft, England, a British companyApplication December 10, 1956, Serial No. 627,479

Claims priority, application Great Britain December 9, 1955 4 Claims.(Cl. 230-45) This invention comprises improvements in or relating tovacuum pumping apparatus.

It is well known to make vacuum pumping apparatus which comprises both adiffusion-pump and a mechanical pump to which the diflusion-pumpdelivers. These are normally connected up by pipework and hand-operatedvalves so that the mechanical suction-pump can be made to first evacuatethe apparatus to which it is connected and thereafter the connectionscan be changed so that the diffusion-pump is brought into operation inseries with the mechanical suction-pump to bring about completeevacuation. It is an object of the present invention to provide anapparatus of this kind in which the construction of the parts and thecontrol of the operations is simplified.

The present invention comprises, in a vacuum pumping apparatus, thecombination of a mechanical suctionpump, a difiusion-pump, an inletvalve to the diiiusionpump, a valve-operating member therefor, andvalved by-pass means also operated by the valve-operating member toconnect the mechanical suction-pump direct to the inlet when desired.

Preferably, the inlet valve to the diffusion-pump, the valve-operatingmember and a by-pass valve forming part of the by-pass means, arelocated in an inlet valve-casing attached to the inlet of thediffusion-pump and are actuated from the exterior by a singleactuating-spindle having a sealed joint with the walls of the casing.The use of a single actuating spindle reduces risk of leakages as wellas involving simplicity of operation.

In the construction hereinafter described by way of example, themechanical suction-pump is located in an oil bath forming the base ofthe apparatus, the diffusionpump is mounted directly upon the said baseand the inlet valve casing is mounted upon the diffusion-pump, the wholeconstituting a self-supporting unit. In such a construction the upperpart of the difiusion-pump and the lower part of the valve casing mayhave interconnected cooling jackets.

Preferably the mechanical suction pump is motor driven by an electricmotor mounted directly upon the oil bath base of the unit. in this way,framing for the apparatus such as is usually employed can be totallyobviated, the control and ipework is simplified and the cfficiency isincreased.

The following is a description by way of example of one construction inaccordance with the invention.

in the accompanying drawings:

Figure l is a side elevation of the apparatus;

Figure 2 is a plan of the valve gear, with cover plate removed andpartly in section;

Figure 3 is a vertical section upon the line 3-3 of Figure 2;

Figure 4 is a section upon the line 4-4 of Figure 2; V Figure 5 is adetail, partly in section upon the line 5-5 of Figure 2; and

Figure 6 is a section on line 66' of Figure 2.

Figure 7 shows the interior of the base.

Figure 8 is' a vertical section of the diffusion pump mounted on thebase.

The apparatus comprises a light-alloy base 11 which forms an oil vesseland contains a mechanical suction pump 12 of the type indicated inFigure 7, comprising a circular casing 13 in which works a circulareccentrically mounted displacer 14 in contact with a sliding vane 15 onone side of which is an inlet 16 and on the other an outlet port 17. Thedisplacer is operated by a crank pin 18 from a shaft which enters thecasing at one side and which extends outside the casing and carries apulley 19. The pulley is driven by a V-belt 112 from an electric motor20 mounted on an inclined face 21 which forms one side of the base ofthe apparatus. The suction-pump works flooded in oil 22 and carries adelivery valve 23 which is beneath the oil surface. It has an adjustableoil inlet 24 on the suction side and the oil which finds its way intothe pump is delivered with the air at the outlet valve, for example asdescribed in my copending application No. 569,005, filed March 2, 1956.

The cast alloy base 11 has a fiat top on which is bolted the base 25 ofa diffusion-pump shown in Figure 8 in section and constructed asdescribed in my copending application No. 627,449, filed December 10,1956, now Patent No. 2,899,126. This pump comprises a stout cylindricalmetal body 26 which is closed at the bottom by a removable plate and issupported so that its lower end is suspended within the heating chamber.An electric heating unit 27 is secured to the bottom of the pump body 26within the heating chamber, and within the pump body there is an oilchamber 23 where oil is heated by the heating unit and from which risetwo concentric vapour tubes 29, 30 carrying diffusion hoods, 31, 32, 33one above the other. The upper part of the pump body is turned to asmaller diameter than the lower part so that the walls are thinner andover this reduced portion there is slid a tubular water jacket casing 34having an outlet 35 at the bottom and an inlet 36 at the top (see Fig.1). Below the water jacket, which extends as far as the lowermost ofthe'three hoods, there is a lateral outlet 37 from the pump body.

The top of the pump body 26 is flanged at 38 and on to the flange thereis bolted a control valve casing 4 the lower part of which is waterjacketed as shown at 41, having an outlet 42 at the bottom which isconnected to the inlet 35 of the diffusion-pump jacket and an inlet 43which is connected to an automaticallyoperated water-flow relay 44. Theoutlet 35 of the diifusion'pump body jacket is connected to drain. Thetop of the control casing 40 has a flange for bolting to the undersideof any apparatus which is to be evacuated.

The control valve casing 40 contains in its lower portion where it isbolted on to the flange 38 of the diffusion-pump, a large circular port45 (Figures 3, 4 and 8) equal in diameter to the interior'of thedifi'usion-pump and surrounded by a circular upstanding seating 46. Onthe seating there seats a disc-valve 47 faced on its underside with arenewable facing 48 of synthetic rubber such as that sold under thetrade name Nygonf? The discvalve not only serves to control the inlet tothe diffusionpump, but when lifted acts as a baffie to hinder thecreeping back into the evacuated space of mists of condensed oilvapours. The top of the diffusion-pump vapour tube assembly also carriesa battle disc 148 (Figure 8) and the baffie disc and the disc-valve,both being located in a water-jacketed portion of the pump, areeflective in of the suctionr-pump,

passage 50 for the gaswhich is being evacuated. This 9 centre of whichis a guide 52 (Figures 3 and 4). The guide serves to guide a cylindricalcamfollower 53, which above the guide carries a' cam-roller 54. Thecamfollower extends below the guide and carries at its lower end thestem 55 of a ball member 56 which is held in a suitable socket on theback of the disc-valve 47. Thus,

pression61 bordered by two flanges V62, 63 projecting laterally from thecam surface on each side. The camfollower 53 of the disc-valve 47engages the underside of the cam surface and it carries two lateral arms64, 65 (Figure 3) which extend upwardly one on each side of thevalve-operating cam 60 and which carrycamrollers 66, 67 projectinginwardly from the arms toward the side surfaces of the valve-operatingcam 60. These cam-rollers are adapted to engage the inner faces of theflanges 62, 63 which border the depression 61 in the cam and when thespindle is rotated sothat the depression comes to the underside of thecam spindle 57, the two cam-rollers on the arms engage the flanges andthe disc-valve 47 is lifted oif its seat. At all other times,constituting about three-quarters of the circumference of the cam thedisc-valve 47 is held firmly closed. The ball stem on thevalve-operating member is adjustable by screwed stem 68 and lock nut69to ensure this. i i

The actuating spindle 57, outside the 'valv'e'body 40, after it haspassed through the seal 59, enters a switchoperating chamber 70 whichcontains two micro switches 71, 72 and earns 73, 74 upon-the spindle foractuating them. The spindle passes on through the switch-operatingchamber to. the exterior thereof Where it carries an operating handle 75having a hub 76 and a pointer 77 cam-follower 53and guide 52 of thedisc-valve 47 which controls the inlet to the diffusion pump. The guide86 is supported on posts 87 carried by a flanged closure 88 for theextension 80. The cam-follower, 84 similarly has a roller 89 to engagethe periphery of the cam 60 and lateral anns 9(l91' with inwardlydirected camrollers 92, 93 to engage behind'the flanges 62, 63 of thecam depression 61; Therefore, if the actuating spindle 57 is rotatedthrough 90 from the point at which the inlet 45 to the difiusion-pump isopen, the diffusion-pump inlet disc-valve 47 will 'be closed and theby-pass discvalve83 will be. opened. If the spindle is rotated through afurther 90, both valves will be'closed.

- Theby-pass pipe 82 from the controlvalve casing 40 is led, downwardlytowards the suction inlet 16 of the mechanical pump.v On its way it isjoined by a horizontal pipe 95 which isconnected to the outlet 37 of thediffupassage is spanned by a'spider 51 (see Figure 2) in the.centricwith the spindle, but which at one side has a de- Y sion-pumpand, below this connection it is provided with r a a, moisture trap 96before it enters the cast base, casting 11 of the apparatus and is.connected to the inlet 16 The outlet, 37 from. the. diffusion-pump isconnected to erated backing-valve 97. There are also provided on thecontrol value casing 4,0, an, air inlet 98 closed by an the by-pass pipe82 through an electro-magnetically-opelectro-magnetically-operatedairadmission valve 99 and on the side of the trap, 96 a furtherelectro-magneticallytype and are connected to the micro switches 71, 72in the switch-operating chamber." A

In operation, when the handle of the-actuating spindle 57 is moved tothe position where both the bypass valve 83 and the inlet'disc-valve' 47are closed,'t h electro-magnetic air admission valves 99, 100 are openedand the pump can be started on no load. on moving the spindle clockwisefrom. the position of Figure 4 the point is reached at which the hy-passvalve 83 is opened and the electro-magnetic air admissionvalves 99-400are closed, and the mechanical suction-pump 13 in the base of theapparatus directly evacuates the apparatus above flange 140 to which thepump is connected. When an adequate vacuum has been reached to operatethe diffusion-pump, by rotating the same operating handle 75 through afurther quadrant of its movement the valve 83 of by-pass 82 can beclosed and the diffusion-pump 26 is brought into use; in this positionthe valve 83 of the by-pass 82 is closed and the disc-valve 47 in theinlet 45 to the diffusion-pump is opened, the backing valve 97 of thediffusion-pump is also opened by the operation of one of the microswitches 71, 72. On rotating the handle 57 through a further quadrant ofits movement all the valves are closed. 7

The electric motor '20 which works the suction pump is started by aseparate switch, and the air-admittance valve to the moisture trap '96and the magnetic valve 97 between the diffusion-pump and the rotary pumpare operated from the same switch as the motor. Thisprotects the plantif the motor is stopped as it isolates the diffusion-pump by closing thebacking valve 97 and at the same time by allowing the air admissionvalve 100 (opened when de-energized) to automatically admit airto 'thesuction side of the rotary pump, The effect is to raise' the pressure toatmospheric and prevent oil being sucked into the system from casing 11if the motor 20 is stopped. V I V The water-flow relay 44 actuatescontacts which are in series with the supply of the current heater 27 ofthe diifusionpump. Should the water-flow through the difiusion-pump beatsubstantially any difierent rate from that for which the water-flowrelay is set, the relay 44 separatessuch contacts and disconnects theelectrical supply from the diffusion-pump heater 27.

I claim:

1. Vacuum pumping apparatus comprising in combinationla base, amechanical suction pump having an inlet and an outlet, and being locatedin an oil bath in the base, an electric motor for driving the mechanicalsuctiop pump and in operative connection therewith, a difl-usion pump onthe base said diffusion pump having an inlet and an outlet, a conduitbetween the diffusion pump outlet and mechanical pump inlet, avalve-casing above the diffusion pump having a valve casing inlet portto the diffusion pump and a valve casing by-pass port, -a bypass fromthe valve casing by-passport to the mechanical pu mp inlet, inlet andby-pass valves for said valve casmeanson the valve casing, said switchmeans closing said backing'valve when the bypass valve is opened, anelectromagnetically actuated air admission valve to the condnit betweenthe diffusion pump and mechanical pump, and a connection from said airadmission valve to the circuit controlling the electric motor, thearrangement being such that if the. motor is stopped the air-admissionvalve is opened, the whole constituting a self-supporting unit.

2. A vacuum pumping apparatus as claimed in claim 1, wherein the upperpart of the diifusion pump and the lower part of the valve casing havinginterconnected cooling jackets.

3. Vacuum pumping apparatus comprising in combination a base, amechanical suction pump located in an oil chamber in the base, a motorin operative connection with the mechanical suction pump for driving thesame, a difiusion-pump secured to the base said diffusion pump having aninlet and an outlet, a valve casing on the inlet to the diffusion-pumphaving a difiusion inlet port communicating with the pump and a by-passport at an angle thereto, an inlet lift-valve for the inlet port, aby-pass valve for the by-pass port, a rotatable valve spindle extendingtransversely to said valves and carrying a cam to operate the same, aby-pass extending from the by-pass port to the mechanical pump inlet, aconduit connecting the delivery of the difiusion pump to the bypass, anelectro-magneticallyactuated backing valve in said conduit, a switch tocontrol said valve located on said valve-casing and a switch-operatingmember on said backing valve spindle to operate the switch.

4. Vacuum pumping apparatus as claimed in claim 3 6 wherein anelectromagnetically-operated airinlet valve is located on the by-pass, asecond switch is located in relation to the said valve spindle, thevalve spindle carries a second switch-operating member to operate thesame, the second switch being connected in a circuit including theair-inlet valve and a connection to the motor circuit, so that the airvalve is opened whenever the valve spindle is placed in an initialposition for starting the motor and whenever the supply to the motorfails.

References Cited in the file of this patent UNITED STATES PATENTS2,063,665 Edwards Dec. 8, 1936 2,289,845 Litton July 14, 1942 2,707,?A9Schneider Apr. 26, 1955 2,721,694 Van Atta Oct. 25, 1955 2,722,371Barrett et a1. Nov. 1, 1955 2,806,644 Warren Sept. 11, 1957 2,826,353Auwarter et a1. Mar. 11, 1958 FOREIGN PATENTS 487,648 Canada Oct. 28,1952 690,649 Great Britain Apr. 22, 1953 719.990 Great Britain Dec. 8,1954

